The goal of Project 4 is to elucidate the separate and combined effects of nanomaterial-based processes and microbial degradation on transformations of target Superfund chemicals, to better understand how nanomaterial-based remediation technologies might be best applied and, to achieve a maximum reduction in toxicity using combined nano-bio remediation. In addition, we seek to understand the potential impacts of nanomaterials themselves on the microbial ecology in sediments. The target contaminants for this study include an organophosphate insecticide (chlorpyrifos), a representative polycyclic aromatic hydrocarbon (benzo[a]pyrene), and a polybrominated flame retardant (decabrominated diphenyl ether, BDE-209). The pervasiveness of these compounds has resulted in a significant need for remediation-strategies to ameliorate their toxicity; however, care must be taken to ensure that remediation techniques do not result in increased toxicity or adverse effects from the use of the technology and/or the degradation products. This project studies remediation using zero valent iron (ZVI) and titanium dioxide (Ti02) nanomaterials for contaminant degradation. Our objectives are to: 1) Investigate the use of nanomaterials as catalysts for direct treatment of sediment and water contaminated by developmental toxicants; 2) Assess microbial degradation of the target contaminants by sediment microorganisms with and without nanomaterials; and 3) Uncover possible synergies (or unintended antagonistic effects) of nanoparticle-based remediation with natural microbial degradation processes.